Combine two integer arrays into one array in java

Question

I've seen similar questions and none provide the answer that I'm looking for, so I apologize in advance if this is considered a duplicate. I'm trying to combine arrays {1, 2, 3} and {4, 5, 6} into {1, 2, 3, 4, 5, 6}. What am I doing incorrectly? I'm super new to java. Sorry if the question is stupid.

public class combine {
  public static void main(String[]args){

  int[]a = {1, 2, 3};
  int[]b = {4, 5, 6};
  int[]c = new int[a+b];
  for(int i=0; i<a.length; i++)
  System.out.print(c[i]+" ");
}
public static int[]merge(int[]a, int[]b){
  int[]c = new int[a.length+b.length];
  int i;
  for(i=0; i<a.length; i++)
     c[i] = a[i];

     for(int j=0; j<b.length; j++)
        c[i++]=b[j];
        return c;
}
}

in some place call merge, and actually is not a merge is like concatenate :P — nachokk
– nachokk, Commented Dec 1, 2013 at 19:59
It's also defined locally in the method; it would never print the correct array. — Jeroen Vannevel
– Jeroen Vannevel, Commented Dec 1, 2013 at 20:00
possible duplicate of How to concatenate two arrays in Java? — Abimaran Kugathasan
– Abimaran Kugathasan, Commented Mar 20, 2014 at 5:18

Sean Patrick Floyd · Accepted Answer · 2013-12-01 20:07:05Z

9

Don't do it yourself, use System.arrayCopy() to copy both arrays into a new array of the combined size. That's much more efficient, as it uses native OS code.

answered Dec 1, 2013 at 20:07

Sean Patrick Floyd

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2 Comments

Kick Buttowski Over a year ago

is it because of deep copying vs shallow copying?

Sean Patrick Floyd Over a year ago

No, both versions are shallow, but System.arrayCopy() uses OS routines instead of Java abstractions.

Alexis C. · Accepted Answer · 2013-12-01 20:04:26Z

6

Instead of

int[]c = new int[a+b];

You need to call your merge method and assign the result to the array like :

int[]c = merge(a,b);

Also you for loop should be :

int[]c = merge(a,b);
for(int i=0; i<c.length; i++)
    System.out.print(c[i]+" ");

edited Dec 1, 2013 at 20:04

answered Dec 1, 2013 at 19:59

Alexis C.

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Comments

Karan singh · Accepted Answer · 2014-12-18 14:03:39Z

5

  String a[] = { "A", "E", "I" };
  String b[] = { "O", "U" };
  List list = new ArrayList(Arrays.asList(a));
  list.addAll(Arrays.asList(b));
  Object[] c = list.toArray();
  System.out.println(Arrays.toString(c));

answered Dec 18, 2014 at 14:03

Karan singh

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2 Comments

StormeHawke Over a year ago

I know the code is pretty clear but it's always best to provide explanation of what you're doing. Plain code with no explanation tends to get flagged for deletion around here. Also - welcome to SO

Karan singh Over a year ago

Thanks @StormeHawke , I am new to this community....will take care in future.... the code was self explanatory so didn't provide comment for it.

zx485 · Accepted Answer · 2016-11-20 21:15:38Z

Please try this code, I hope it's useful for you

String a[] = new String[4];
    String b[] = new String[2];
    String[] ab = new String[a.length + b.length];
    int i, j, d, s = 0;
    @SuppressWarnings("resource")
    Scanner x = new Scanner(System.in);
    System.out.println("Enter the first array");

    for (i = 0; i < a.length; i++) {
        a[i] = x.next();
        for (d = i; d < a.length; d++) {
            ab[d] = a[i];
        }
    }

    System.out.println("Enter the second array");

    for (j = 0; j < b.length; j++) {
        b[j] = x.next();
        for (d = a.length + j; d < ab.length; d++)
            ab[d] = b[j];
    }
    System.out.println();
    System.out.println("The new array is !!");
    System.out.println("--------------------");
    for (s = 0; s < ab.length; s++) {
        System.out.print(ab[s] + " ");
    }

Ijhar Ansari · Accepted Answer · 2018-01-28 04:05:48Z

1

class MerginTwoArray{
public static void mergingarr(int x[], int y[])
{
    int len=x.length+y.length;
    int arr[]=new int[len];
    //create a variable j which will begin zeroth index of second array
    int j=0;
    for(int i=0; i<arr.length; i++)
    {
        if(i<x.length)
        {
            arr[i]=x[i];
        }
        else
        {
            arr[i]=y[j];
            j++;
        }
    }
    for(int i:arr)
    {
        System.out.print(i+ " ");
    }
}
public static void main(String... args)
{
    mergingarr(new int[]{1,2,3}, new int[]{4,5,6});
}

}

Hope this is clear to you

answered Jan 28, 2018 at 4:05

Ijhar Ansari

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Comments

Stephen Rauch · Accepted Answer · 2018-10-25 03:52:29Z

1

One more way of concatenating 2 arrays is:

System.out.println("Enter elements for a: ");
for (int i = 0; i < 5; i++) {
    int num = in.nextInt();
    a[i] = num;
}

System.out.println("Enter elements for b: ");
for (int i = 0; i < 5; i++) {
    int num = in.nextInt();
    b[i] = num;
}

void merge() {
    int c[] = new int[10];
    System.arraycopy(a, 0, c, 0, a.length);
    System.arraycopy(b, 0, c, a.length, b.length);

    System.out.println(Arrays.toString(c));  // merged array 
}

edited Oct 25, 2018 at 3:52

Stephen Rauch♦

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answered Oct 25, 2018 at 3:31

Mahen Gandhi

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Comments

PeterSW · Accepted Answer · 2016-01-20 12:52:08Z

0

You can use the following:

package array;

public class Combine {

public static void main(String[] args) {

 int[]a = {1,2,3,4};
 int[]b = {4,16,1,2,3,22};
 int[]c = new int[a.length+b.length];
 int count=0;

  for(int i=0; i<a.length; i++)
    {
       c[i]=a[i];
       count++;
    }

 for(int j=0;j<b.length;j++)
    {
       c[count++]=b[j];
    }

        for(int i=0;i<c.length;i++)
        System.out.print(c[i]+" ");
}

}

edited Jan 20, 2016 at 12:52

PeterSW

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answered Jan 20, 2016 at 12:46

Siddharth Singh Rawat

1

Comments

Mona Jalal · Accepted Answer · 2016-05-25 07:45:50Z

0

Have a look at my solution (you can eventually sort it if need be):

public static int[] mergeAndSortIntArrays(int[] firstInt, int[] secondInt){

    List<Integer> merged = new ArrayList<>();

    for (int i=0; i<firstInt.length; i++){
        merged.add(firstInt[i]);
    }

    for (int i=0; i<secondInt.length; i++){
        merged.add(secondInt[i]);
    }

    Collections.sort(merged);
    int[] result=new int[merged.size()];
    for (int i=0; i<merged.size(); i++){
        result[i]=merged.get(i);
    }
    return result;
}

answered May 25, 2016 at 7:45

Mona Jalal

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Comments

user6012628 · Accepted Answer · 2016-09-20 06:37:28Z

0

   int a[] = {
        5, 10, 15, 25
    };
    int b[] = {
        12, 5, 7, 9
    };
    int c[] = new int[8];
    for (int i = 0; i < 4; i++) {
        System.out.println(a[i]);

    }
    System.out.println("**************");
    for (int j = 0; j < 4; j++) {
        System.out.println(b[j]);
    }
    //int[] c=merge(a,b);
    for (int i = 0; i < 4; i++) {

        c[i] = a[i];

    }
    for (int i = 0; i < 4; i++) {
        for (int k = 4; k < 8; k++) {
            c[k] = b[i];
        }

    }
    for (int i = 0; i < 4; i++) {
        System.out.println(c[i]);
    }

answered Sep 20, 2016 at 6:37

user6012628

1 Comment

TobiasR. Over a year ago

Some explanation would be nice.

Shihab Uddin · Accepted Answer · 2019-07-03 08:58:53Z

0

Merge two array without arraylist.

    public class Main {


    static int a[] = {1, 2, 3, 4};
    static int b[] = {5, 6, 7, 8};

    public static void main(String[] args) {

        System.out.println("Hello World!");
        int totalLengh = a.length + b.length;

        int c[] = new int[totalLengh];

        int j = 0;
        for (int i = 0; i < totalLengh; i++) {

            if (i < a.length) {

                c[i] = a[i];

            } else {
                c[i] = b[j];
                j++;
            }

            System.out.println("" + c[i]);
        }
    }
}

answered Jul 3, 2019 at 8:58

Shihab Uddin

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Comments

Bablu kumar · Accepted Answer · 2017-12-19 06:45:27Z

-1

 public class MergeArrays {
    public static void main(String[]args){
         int[] a = {1, 2, 3};
         int[] b = {4, 5, 6};
         int[] c = new int[a.length+b.length];// Here length of int[] c will be 6
         int count = 0;

         //looping to store the value length of i
         for(int i = 0; i<a.length; i++) { 
             c[i] = a[i];
             count++;
          }
        //looping to store the value length of j
          for(int j = 0;j<b.length;j++) { 
             c[count++] = b[j];
          }
        //looping to retrieve the value of c
          for(int i = 0;i<c.length;i++) 
              System.out.print(c[i]);// Displaying looped value/output in single line at console 

    }
}

edited Dec 19, 2017 at 6:45

answered Dec 4, 2017 at 10:04

Bablu kumar

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Comments

Sanyam Thukral · Accepted Answer · 2016-09-27 20:21:15Z

-3

public static void main(String[]args){

        int[]a = {1, 2, 3};
        int[]b = {4, 5, 6};
        int[]c ;
        c=merge(a,b);
        for(int i=0; i<c.length; i++)
            System.out.print(c[i]+" ");
    }
    public static int[]merge(int[]a, int[]b){
        int[]c = new int[a.length+b.length];
        int i;
        for(i=0; i<a.length; i++)
            c[i] = a[i];
        System.out.println(i);
        for(int j=0; j<b.length; j++)
            c[i++]=b[j];
        return c;
    }

edited Sep 27, 2016 at 20:21

user6655984

answered Sep 27, 2016 at 19:03

Sanyam Thukral

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